Anchoring groups for dye-sensitized
solar cells (DSSCs) play a
decisive role in high-power conversion efficiency (η) and long-term
cell durability. To date, a carboxylic acid is the most widely used
anchoring group for DSSCs. However, the carboxylic acid tends to dissociate
from a TiO2 surface during the cell operation as well as
in the presence of water. Considering that the dye dissociation from
TiO2 leads to a decrease in the cell performance, stable
anchoring groups are highly desirable to achieve long-term durability
of DSSCs toward their practical application. In this study, we designed
and synthesized a series of porphyrin dyes with the triethoxysilyl
anchoring groups, ZnPSi1, ZnPSi2, and ZnPSi3, to evaluate the effects of the silicon-based anchoring
group on cell durability and photovoltaic properties. The DSSCs based
on ZnPSi1, ZnPSi2, and ZnPSi3 exhibited moderate η-values of 2.2, 4.7, and 2.3%, respectively.
It is noteworthy that the η-value of the DSSC based on ZnPSi2 (4.7%) is the highest among DSSCs based on porphyrin
dyes with silicon-based anchoring groups. The moderate η-values
are mainly attributed to the low charge collection efficiency originating
from the low surface coverage and plausible tilted geometry of the
dyes on TiO2. More importantly, we demonstrated that the
DSSC based on ZnPSi2 revealed higher long-term cell durability
under illumination than that based on reference porphyrin YD2-o-C8 having a conventional
carboxylic acid anchoring group.